Patent application title: OPTICAL STORAGE MEDIUM AND PLAYER

Abstract:

An optical storage medium that allows the user to recognize a given disk
as a hybrid one, no matter whether the disk is loaded into a single
format player or a multi-format player, is provided. The optical storage
medium includes a stack of first and second storage layers with mutually
different storage densities. Management information indicating the
presence of the second storage layer is stored on the first storage
layer.

Claims:

1. An optical storage medium comprising a stack of first and second
storage layers with mutually different storage densities,wherein
management information indicating the presence of the second storage
layer is stored on the first storage layer.

2. The optical storage medium of claim 1, wherein the first storage layer
has a lead-in area, andwherein the management information is stored in
the lead-in area of the first storage layer.

3. The optical storage medium of claim 2, wherein user data indicating the
presence of the first storage layer is stored on the second storage
layer.

4. The optical storage medium of claim 3, wherein the second storage layer
has a lead-in area, andwherein the user data is not stored in the lead-in
area of the second storage layer but in a different area of thereof.

5. The optical storage medium of claim 3, wherein the second storage layer
further has a data area, andwherein the user data is stored in the data
area of the second storage layer.

6. The optical storage medium of claim 5, wherein the user data relates to
at least one of video and audio indicating the presence of the first
storage layer.

7. The optical storage medium of claim 5, wherein sequence information
defining a procedure of processing to be carried out first when data is
read out from the second storage layer is stored in the data area of the
second storage layer, andwherein the sequence information defines the
procedure of presenting video based on the video data.

8. The optical storage medium of claim 3, wherein each of the first and
second storage layers has a data area, andwherein a first piece of title
information about a content of a first quality and a first piece of
copyright management information for protecting the copyright of the
content of the first quality are stored in the data area of the first
storage layer, andwherein a second piece of title information about a
content of a second quality and a second piece of copyright management
information for protecting the copyright of the content of the second
quality are stored in the data area of the first storage layer.

9. The optical storage medium of claim 8, wherein the first and second
pieces of copyright management information define mutually different
copyright protection conditions.

10. A player for retrieving information from an optical storage medium,
the optical storage medium comprising a stack of first and second storage
layers with mutually different storage densities, management information
indicating the presence of the second storage layer being stored on the
first storage layer, the player comprising:a reading section for reading
the management information when the player is loaded with the optical
storage medium; anda control section for outputting information
indicating the presence of the second storage layer based on the
management information.

11. The player of claim 10, wherein the first storage layer has a lead-in
area in which the management information is stored and a data area in
which user data about at least one of video and audio indicating the
presence of the second storage layer is stored, andwherein the reading
section further reads the user data, andwherein the control section
outputs at least one of video and audio based on the user data, thereby
making a notification of the presence of the second storage layer.

12. The player of claim 10, wherein the second storage layer has a data
area in which user data about at least one of video and audio indicating
the presence of the first storage layer is stored, andwherein the reading
section further reads the user data from the second storage layer,
andwherein the control section outputs at least one of video and audio
based on the user data of the second storage layer, thereby making a
notification of the presence of the first storage layer.

13. A player for retrieving information from an optical storage medium,
the optical storage medium comprising a stack of first and second storage
layers with mutually different storage densities, video information of a
first definition being stored on the first storage layer, video
information of a second definition being stored on the second storage
layer, the player comprising:a memory that stores in advance output
information specifying definition of video to output;a control section
for selecting, in accordance with the output information, either the
first storage layer or the second storage layer to read video information
from when the player is loaded with the optical storage medium; anda
reading section for reading the video information from the first or
second storage layer selected.

14. The player of claim 13, further comprising an interface section that
receives information, specifying a signal format acceptable for an output
device, as the output information from a user.

15. The player of claim 13, further comprising an interface section that
receives information, specifying a signal format acceptable for an output
device, as the output information from the output device.

Description:

TECHNICAL FIELD

[0001]The present invention relates to an optical storage medium including
multiple types of storage layers with mutually different storage
densities and also relates to a player for selecting one of those storage
layers of such a storage medium and retrieving information from that
storage layer.

BACKGROUND ART

[0002]Various types of optical information storage media (which will also
be referred to herein as "optical storage media"), including CDs and
DVDs, have been developed.

[0003]Recently, an optical disk including multiple storage layers with
mutually different storage densities (or recording formats), i.e., a
so-called "hybrid disk", has been put on the market. For example, Patent
Document No. 1 discloses a hybrid disk including a storage layer that
uses the same format as CDs (which is called a "CD layer") and a storage
layer that uses the same format as DVDs (which is called a "DVD layer").
On the other hand, Patent Document No. 2 discloses a hybrid disk
including a storage layer that uses the same format as a high definition
(HD) disk containing audio information (which is called an "HD layer")
and a CD layer.

[0004]As these hybrid disks have been developed, a player that can
retrieve information from any of those storage layers of a hybrid disk
(which is called a "multi-format player") has also been developed. Those
storage layers with mutually different storage densities have different
physical shapes, and therefore, have an optical difference, too. The
multi-format player can sense that difference, recognize the desired
storage layer and perform an appropriate type of signal processing
according to the information stored on that layer, thereby retrieving the
information. Patent Document No. 2 discloses such a player.

[0005]One of the advantages of the hybrid disk is that the disk allows
even a player compliant with only one format (which is called a "single
format player") to retrieve information from it. For example, even a CD
player and a DVD player, both of which are single-format players, can
retrieve information from the hybrid disk disclosed in Patent Document
No. 1. That is to say, a CD player could read information from the CD
layer and a DVD player could read information from the DVD layer.

[0006]However, the optical properties of each layer of the hybrid disk are
not always the same as those of the only storage layer of an optical
disk. That is why if a hybrid disk were loaded by mistake into a player
that is not compatible with hybrid disks, the laser beam might be
accidentally focused on one of its storage layers. In that case, the
player might cause a failure.

[0007]To overcome such a problem, Patent Document No. 3 discloses a method
for preventing a conventional player from malfunctioning in a situation
where a dual-layer disk is loaded into the player. The dual-layer disk
disclosed in Patent Document No. 3 includes a storage layer corresponding
to that of a conventional CD (which is called a "low-density storage
layer") and another storage layer with higher density. In a predetermined
area of the high-density storage layer, a piece of information indicating
that this is not a CD (i.e., information that is not defined by CD's
signal format) is stored at such a low storage density as to be easily
read even by a CD player. By storing such a piece of information, even if
the laser beam happened to be focused on the high-density storage layer,
the playback operation of the player would stop halfway. Consequently, it
is possible to prevent the CD player from malfunctioning.

[0011]When loaded with a hybrid disk, a single format player can recognize
its compatible storage layer but never recognizes the other storage layer
or notifies the user of the presence. That is why the user may not
recognize the disk as a hybrid disk properly. In that case, even when he
or she purchases a player that can retrieve information from that other
storage layer, he or she will not imagine that unknown information is
retrievable from that disk.

[0012]In such a situation, it would be very inconvenient for the user if
the package or label of the disk were the only means for identifying the
disk for him or her. It is also unrealistic for him or her to always get
multiple types of single-format players ready to see whether the given
disk is a hybrid one or not.

[0013]Meanwhile, when a multi-format player is used, it takes a lot of
time to get a loaded disk ready to play, which is also a problem.

[0014]For example, when loaded with a disk, a player sees if every storage
layer of the disk is accessible and determines whether the disk is a
hybrid one or not. It also takes a rather long time to get this
processing done, and therefore, the user has to wait a long time before
the player gets ready to be play the disk.

[0015]On top of that, the conventional multi-format player does not allow
the user to decide, according to the playing environment or his or her
preference, from which storage layer information should be retrieved
first. That is why the user may sometimes have to suspend playback for a
while to make a selection, and he or she will have to wait a long time
before he or she can retrieve his or her desired information.

[0016]This problem will be described in further detail by way of a
specific example. Suppose high definition (HD) compressed data of a movie
is stored on the high-density storage layer of a hybrid disk and standard
definition (SD) compressed data of the same movie is stored on the
standard density storage layer thereof. If the user is now using an HD
compatible appliance such as an HD digital TV set, the player may play
back the HD quality movie from the high-density storage layer. However,
if he or she is using an SD compatible appliance such as a conventional
NTSC analog TV set, then he or she has to stop the output of the HD
quality movie once and then switch the outputs into an SD quality movie,
which is very inconvenient for him or her. Also, according to the
settings of the device installed, processing of converting HD quality
into SD quality could start automatically, and the SD quality produced by
the conversion might be inferior to that of the standard density storage
layer of the hybrid disk.

[0017]Also, music, image, video or any other copyrighted work may be
distributed, or its copy generation may be managed, on different
conditions according to its quality. For example, in a situation where
the same movie or music clip is stored as standard quality compressed
data and high quality compressed data on the standard density storage
layer and the high-density storage layer, respectively, the distribution
and copy generation management are preferably controlled under
respectively different conditions.

[0018]An object of the present invention is to provide an optical storage
medium, a player and a playback method that allow the user to recognize a
given disk as a hybrid one, no matter whether the disk is loaded into a
single format player or a multi-format player. Another object of the
present invention is to make a multi-format player select a storage layer
to retrieve information from either automatically according to the
playback environment or at the user's request, thereby starting to
retrieve desired information as quickly as possible.

Means for Solving the Problems

[0019]An optical storage medium according to the present invention
includes a stack of first and second storage layers with mutually
different storage densities. Management information indicating the
presence of the second storage layer is stored on the first storage
layer.

[0020]The first storage layer may have a lead-in area, and the management
information may be stored in the lead-in area of the first storage layer.

[0021]User data indicating the presence of the first storage layer may be
stored on the second storage layer.

[0022]The second storage layer may have a lead-in area, and the user data
may not be stored in the lead-in area of the second storage layer but in
a different area of thereof.

[0023]The second storage layer may further have a data area, and the user
data may be stored in the data area of the second storage layer.

[0024]The user data may relate to at least one of video and audio
indicating the presence of the first storage layer.

[0025]Sequence information defining a procedure of processing to be
carried out first when data is read out from the second storage layer may
be stored in the data area of the second storage layer. The sequence
information may define the procedure of presenting video based on the
video data.

[0026]Each of the first and second storage layers may have a data area. A
first piece of title information about a content of a first quality and a
first piece of copyright management information for protecting the
copyright of the content of the first quality may be stored in the data
area of the first storage layer. A second piece of title information
about a content of a second quality and a second piece of copyright
management information for protecting the copyright of the content of the
second quality may be stored in the data area of the first storage layer.

[0027]The first and second pieces of copyright management information may
define mutually different copyright protection conditions.

[0028]A player according to the present invention retrieves information
from an optical storage medium. The optical storage medium includes a
stack of first and second storage layers with mutually different storage
densities, and management information indicating the presence of the
second storage layer is stored on the first storage layer. The player
includes: a reading section for reading the management information when
the player is loaded with the optical storage medium; and a control
section for outputting information indicating the presence of the second
storage layer based on the management information.

[0029]The first storage layer may have a lead-in area in which the
management information is stored and a data area in which user data about
at least one of video and audio indicating the presence of the second
storage layer is stored. The reading section may further read the user
data. And the control section may output at least one of video and audio
based on the user data, thereby making a notification of the presence of
the second storage layer.

[0030]The second storage layer may have a data area in which user data
about at least one of video and/or audio indicating the presence of the
first storage layer is stored. The reading section may further read the
user data from the second storage layer. And the control section may
output at least one of video and audio based on the user data of the
second storage layer, thereby making a notification of the presence of
the first storage layer.

[0031]Another player according to the present invention retrieves
information from an optical storage medium. The optical storage medium
includes a stack of first and second storage layers with mutually
different storage densities. Video information of a first definition is
stored on the first storage layer, while video information of a second
definition is stored on the second storage layer. The player includes: a
memory that stores in advance output information specifying definition of
video to output; a control section for selecting, in accordance with the
output information, either the first storage layer or the second storage
layer to read video information from when the player is loaded with the
optical storage medium; and a reading section for reading the video
information from the first or second storage layer selected.

[0032]The player may further include an interface section that receives
information, specifying a signal format acceptable for an output device,
as the output information from a user.

[0033]Alternatively, the player may further include an interface section
that receives information, specifying a signal format acceptable for an
output device, as the output information from the output device.

EFFECTS OF THE INVENTION

[0034]An optical storage medium according to the present invention
includes two storage layers with mutually different storage densities,
and one of the two storage layers stores management information
indicating the presence of the other storage layer. And if the player
notifies the user of the presence of the other storage layer based on
this management information, he or she can sense the presence of that
layer easily.

[0035]In particular, according to the present invention, the management
information is stored in the lead-in area of the first storage layer and
user data indicating the presence of the first storage layer is also
stored in the data area of the second storage layer. Any type of
information may be stored in the data area. For that reason, even if the
data structure of the second storage layer is defined by a standard, for
example, the player can still interpret that information and present its
contents to the user. Consequently, he or she can sense the presence of
the additional layer, no matter whether the player can retrieve
information from only the first storage layer or only the second storage
layer.

BRIEF DESCRIPTION OF DRAWINGS

[0036]FIG. 1 illustrates the multilayer structure of an optical disk 100
according to a preferred embodiment of the present invention.

[0074]Hereinafter, preferred embodiments of the present invention will be
described with reference to the accompanying drawings.

[0075]In the following description of preferred embodiments, the
information storage medium is supposed to be an optical storage medium
(which will be referred to herein as an "optical disk"). The optical disk
is supposed to be a read-only one in the following description.

[0076]Also, the optical disk is supposed to be a hybrid disk including a
stack of two storage layers with mutually different storage densities.
The information stored in each of these two storage layers is read
optically with a light beam that has been emitted from a semiconductor
laser diode. It should be noted that no single storage layer is supposed
to have a plurality of storage areas with different storage densities.

[0077]Various types of storage layers may be combined with each other. In
the following example, a storage layer, of which the format is compatible
with DVDs and which will be referred to herein as a "low-density storage
layer", and another storage layer, of which the format is compatible with
BDs and which will be referred to herein as a "high-density storage
layer", are used in combination. The low-density storage layer has a
storage capacity of less than 5 GB (e.g., 4.7 GB) and the high-density
storage layer has a storage capacity of 20 GB or more (e.g., 25 GB).

[0078]Hereinafter, the physical structure and the data structure of an
optical disk according to a preferred embodiment of the present invention
will be described specifically with reference to FIGS. 1 to 3.

[0079]FIG. 1 illustrates the multilayer structure of an optical disk 100
according to a preferred embodiment of the present invention. The optical
disk 100 includes a protective glass layer 101, a high-density storage
layer 102, a base member 103, a low-density storage layer 104, and
another base member 105, which are stacked in this order. Among these
members, information is stored on the high-density storage layer 102 and
the low-density storage layer 104.

[0080]In reading information from the optical disk 100, the disk 100 is
irradiated with a light beam that has come from under (or over), and been
transmitted through, the protective glass layer 101. FIG. 1 shows a light
beam 110-1 focused on the high-density storage layer 102 and another
light beam 110-2 focused on the low-density storage layer 104 just for
reference.

[0081]Hereinafter, the low-density storage layer 104 will be described
first, and then the high-density storage layer 102 will be described.

[0082]The low-density storage layer 104 is located at a depth of 0.6 mm as
measured from the disk surface on the light beam incoming side. The
low-density storage layer 104 is arranged at that depth so as to be
compatible with normal DVDs.

[0083]A DVD is formed by bonding together a transparent substrate
including an information storage layer and having a thickness of 0.6 mm
and a base member with a thickness of 0.6 mm. And a series of concave and
convex pits are arranged thereon spirally at an interval of approximately
0.7 μm. The light beam is transmitted through the substrate with a
thickness of 0.6 mm to irradiate the information storage layer.
Consequently, information is read as a variation in the intensity of the
reflected light.

[0084]That is why the low-density storage layer 104 is also arranged at
the same depth as the DVD's storage layer and also retains information
that is stored spirally at an interval of approximately 0.7 μm. The
information stored on the low-density storage layer 104 is read with a
red light beam 110-2 with a wavelength of about 660 nm.

[0085]On the other hand, the high-density storage layer 102 is located at
a depth of approximately 0.1 mm as measured from the disk surface on the
light beam incoming side so as to be compatible with BDs. This depth of
0.1 mm is equal to the thickness of the protective glass layer 101. The
base member 103 with a thickness of 0.5 mm is sandwiched between the
high-density storage layer 102 and the low-density storage layer 104. As
a result, the light beam focused on the low-density storage layer 104 is
less likely to be affected by the high-density storage layer 102, which
is located away from the focal point.

[0086]The high-density storage layer 102 achieves storage density that is
approximately five times as high as that of the low-density storage layer
104 and DVDs. For that purpose, information is also stored as spiral
concave and convex pits at an interval of approximately 0.3 μm. The
pit length of the high-density storage layer 102 is shorter than that of
the low-density storage layer 104. The information stored on the
high-density storage layer 102 is read with the light beam 110-1, which
is transmitted through the protective glass layer 101 with a thickness of
0.1 mm and irradiates the high-density storage layer 102. As a result,
the information is read as a variation in the intensity of the reflected
light.

[0087]It should be noted that the protective glass layer 101 is actually
often made of a resin and does not have to be made of glass, strictly
speaking. Also, to read information from the low-density storage layer
104, the high-density storage layer 102 needs to be semi-transparent and
transmits light at a predetermined ratio. The protective glass layer 101
and the base member 103 are transparent. The base member 105 has a
thickness of 0.6 mm.

[0088]Next, the data structures of the high-density storage layer 102 and
low-density storage layer 104 will be described with reference to FIG. 2.

[0089]FIG. 2(a) shows the data structure of the high-density storage layer
102, while FIG. 2(b) shows that of the low-density storage layer 104.
Different data structures compliant with the BD and DVD standards,
respectively, are defined for these layers. In each of FIGS. 2(a) and
2(b), the direction in which these areas are arranged from left to right
on the paper corresponds to the direction in which they are actually
arranged from the inner edge toward the outer edge on the optical disk
100.

[0090]Referring to FIG. 2(a), arranged on the high-density storage layer
102 are a lead-in area 201, a data area 202, and a lead-out area 203.

[0091]The lead-in area (which will be simply referred to herein as a
"lead-in") 201 is arranged as the innermost area such that an information
retrieval device can access that area most quickly when loaded with an
information storage medium. The lead-in is provided to not only make the
player perform stabilized tracking but also store physical control
information.

[0092]In the lead-in 201 of the high-density storage layer 102, stored is
a piece of management information (which will be referred to herein as
"hybrid information") 21 indicating that the optical disk 100 has another
storage layer that has a different storage density from the high-density
storage layer 102. In this preferred embodiment, a value indicating the
presence of the low-density storage layer 104 is given as the hybrid
information 21, which will be described in further detail later with
reference to FIG. 3.

[0093]In the data area 202, stored are volume information 2021, navigation
information 2022 and high definition (HD) title information 2023. The
volume information 2021 shows a file structure. The navigation
information 2022 is control information such as the order of presentation
of a content. The HD title information 2023 is compressed digital data
about high-definition video (HD video). Specifically, the navigation
information 2022 includes content's copyright management information 2024
about the HD title information 2023. The copyright management information
2024 includes copy control information and may be used to make the HD
title information 2023 "copying prohibited", "copying permitted one
generation only", "copying permitted without restrictions" or
"distribution prohibited", for example.

[0094]The lead-out area (which will be simply referred to herein as a
"lead-out") 203 is provided mainly to make the player perform stabilized
tracking.

[0095]Next, referring to FIG. 2(b), the data structure of the low-density
storage layer 104 also includes a lead-in 211, a data area 212 and a
lead-out 213. The lead-in 211 and the lead-out 213 are provided for the
same purposes as the counterparts of the high-density storage layer 102.

[0096]However, the lead-in 211 of the low-density storage layer 104
includes no information corresponding to the hybrid information 21 so as
to be compliant with the DVD standard. That is to say, the DVD standard
does not require providing information corresponding to the hybrid
information 21 for the lead-in. That is why if such a type of information
were included, then the information stored on the low-density storage
layer 104 would no longer be retrievable for a conventional (DVD) player.
Thus, to guarantee playback using a conventional DVD player, no
information corresponding to the hybrid information 21 is stored in the
lead-in 211.

[0097]Meanwhile, in the data area 212, stored is a piece of information
indicating the presence of another storage layer with a different storage
density (i.e., the high-density storage layer 102). Hereinafter, the data
area 212 will be described in further detail.

[0099]The volume information 2121 shows a file structure. The navigation
information 2122 is control information such as the order of presentation
of a content. The SD title information 2123 is compressed digital data
about standard-definition video. Specifically, the navigation information
2122 includes copyright management information 2124 about the SD title
information 2123. It should be noted that the copyright management
information 2124 is provided for a content with the SD title information
2123, unlike the copyright management information 2024 for a content with
the HD title information 203.

[0100]In this preferred embodiment, the HD title information 2023 and the
SD title information 2123 are about the same content with different
qualities. That is why by providing respective pieces of copyright
management information for these pieces of title information for two
different qualities, the distribution condition and copy generation
management are controllable as if they were two different contents. For
that reason, the copyright management information 2024 for the HD title
information 2023 and the copyright management information 2124 for the SD
title information 2123 do not have to include the same contents but may
have totally different contents.

[0101]In the data area 212, further stored is HD presence information
2125, which indicates the presence of the high-density storage layer 102,
or speaking more directly, that HD audio/video information is stored on
this optical disk 100. This HD presence information 2125 is video
information or audio information compliant with an MPEG standard, which
can be read by a normal DVD player, for example. That is to say, this HD
presence information 2125 is treated as normal video information or audio
information that has been written on a data area where any type of
information can be stored. The video information or audio information
that is stored as the HD presence information 2125 is presented while a
program sequence called "First Play PGC" is being executed.

[0102]The following Table 1 shows the data specifications of an HD title,
while the following Table 2 shows those of an SD title. The amount of
information that can be stored on the high-density storage layer 102 is
approximately five times as large as that of the low-density storage
layer 104. That is why video (e.g., a moving picture among other things)
with a greater number of pixels can be stored on the high-density storage
layer 102.

[0103]The HD title information 2023 may be stored in the format of an MPEG
transport stream, for example. An MPEG transport stream includes at least
video stream packets and audio stream packets that are multiplexed
together.

[0104]As shown in Table 1, the video stream of the HD title is encoded
compliant with either the MPEG-2 standard or the MPEG-4 standard. The
maximum numbers of pixels of the video are 1,920 horizontally and 1,080
vertically. Likewise, the audio stream of the HD title is encoded
compliant with the AAC standard with high affinity for a digital
broadcast.

[0105]On the other hand, the SD title information 2123 may be stored in
the format of an MPEG program stream, for example. An MPEG program stream
includes video stream packets (or packs) and audio stream packets (or
packs) that are multiplexed together.

[0106]As shown in Table 2, the video stream of the SD title is encoded
compliant with the MPEG-2 standard. The maximum numbers of pixels of the
video are 720 horizontally and 480 vertically. Likewise, the audio stream
of the SD title is encoded compliant with the AC-3 standard.

[0107]In this preferred embodiment, the HD title and the SD title are
about the same content with different audio/video qualities. The video
quality is proportional to the magnitude of the bit rate. For example, HD
video has a maximum bit rate of 34 Mbps and SD video has a maximum bit
rate of 10 Mbps. Since video has higher resolution than audio, video
includes a greater amount of information than audio.

[0108]The high-density storage layer 102 has a sufficient data storage
capacity. That is why an additional content, which is not present on the
low-density storage layer 104 (i.e., a so-called "bonus content"), is
sometimes stored on the high-density storage layer 102.

[0109]Next, the hybrid information 21 will be described in detail with
reference to FIG. 3, which shows correlation between the lead-in 201 of
the high-density storage layer 102 and the hybrid information 21.

[0110]The lead-in 201 is subdivided into various areas, one of which is
called permanent information and control data (PIC) area 2011. The PIC
area 2011 includes more than one disk information (DI) area #1, . . . and
#n. And the hybrid information 21 is stored at a predetermined data
location within the DI area #1 2012.

[0111]The hybrid information 21 may have any specific data structure as
long as the information can indicate whether the low-density storage
layer 104 is present or not. For example, hybrid information 21 "00" may
indicate that there is no low-density storage layer 104, i.e., the
optical disk is not a hybrid disk, while hybrid information 21 "01" may
indicate the presence of the low-density storage layer 104.
Alternatively, the two-bit value may be replaced with a simple one-bit
value, too.

[0112]The hybrid information 21 may have the value "00" indicating that
the disk is not a hybrid disk because a non-hybrid disk such as a BD-ROM
could store the hybrid information 21, too. The high-density storage
layer 102 of a hybrid disk and the storage layer of a BD-ROM may have the
same data structure. That is why the player can recognize the type of the
given disk by the value of the hybrid information.

[0113]Hereinafter, the configuration and operation of an apparatus that
can retrieve information from the optical disk 100 described above will
be described with reference to FIG. 4.

[0114]FIG. 4 shows the configuration of a player 300 according to this
preferred embodiment. A TV set 320 connected to the player 300 is also
shown in FIG. 4. The player 300 and the TV set 320 are connected together
via an HDMI cable 330.

[0115]The player 300 can retrieve information from respective layers of
the optical disk 100 including the high-density storage layer 102 and the
low-density storage layer 104. When loaded with the optical disk 100
inserted, the player 300 reads various sorts of information from the
optical disk 100 and then outputs video information and audio information
at such qualities that the TV 321 and loudspeakers 322 of the TV set 320
can deal with.

[0116]It should be noted that the player 300 could also retrieve
information from a normal DVD with the same storage density as the
low-density storage layer 104 and from a BD with the same storage density
as the high-density storage layer 102.

[0118]Among these components, the optical pickup 310, the user input I/F
316, the video output format memory 317 (which will be simply referred to
herein as a "format memory 317) and the connection I/F 318 are provided
as independent pieces of hardware. The HD decoder 3140 and the SD decoder
3150 may be provided as either independent decoder circuits (or chips) or
a single decoder chip also including the signal switching section 313.
Alternatively, the HD decoder 3140 and the SD decoder 3150 may share part
of their processors.

[0119]On the other hand, the layer recognizing section 311, the layer
specifying section 312, the signal switching section 313 and the
copyright information processing section 319 may be provided as
respectively independent dedicated circuits. Or the CPU 301 may perform
the functions of these components (which will be described in detail
later) by executing a computer program, for example. For the sake of
simplicity, those components are shown in FIG. 4 separately from the CPU
301.

[0120]Hereinafter, the functions of the respective components will be
described one by one.

[0121]The CPU 301 controls the overall operation of the player 300.

[0122]The general-purpose memory 302 is a known random access memory (RAM)
and stores a computer program, temporary data and so on when the CPU 301
is operating.

[0123]The optical pickup 310 emits a light beam toward the optical disk
100 and focuses it on either the high-density storage layer 102 or the
low-density storage layer 104. Also, the optical pickup 310 performs
tracking so as to follow the tracks on the high-density storage layer 102
or the low-density storage layer 104, and reads information from the
high-density storage layer 102 or the low-density storage layer 104,
thereby outputting a read signal.

[0124]The layer recognizing section 311 determines, based on the read
signal supplied from the optical pickup 310, whether the layer on which
the light beam is currently focused and which is being tracked by the
optical pickup 310 now is the low-density storage layer 104 or the
high-density storage layer 102.

[0125]In accordance with the decision made by the layer recognizing
section 311 and the contents of the format memory 317, the layer
specifying section 312 determines the storage layer to retrieve
information from and instructs the optical pickup 310 which storage layer
the light beam should be focused on. The layer specifying section 312
also instructs the signal switching section 313 to switch the read
signals.

[0126]The signal switching section 313 switches the transmission paths of
the read signal supplied from the optical pickup 310, thereby selecting
either the HD decoder 3140 or the SD decoder 3150 to process the signal.
If the player 300 is loaded with the optical disk 100, the signal
switching section 313 may switch the transmission paths not just when
information should start to be read but also at an arbitrary time as
well. Specifically, if the player 300 is loaded with a BD, the signal
switching section 313 switches the paths into a playback path leading to
the HD decoder 3140 when information starts to be read. On the other
hand, if the player 300 is loaded with a DVD, the signal switching
section 313 switches the paths into a playback path leading to the SD
decoder 3150.

[0127]In FIG. 4, the signal switching section 313 is shown as a hardware
switch. However, this is just an example to make the function of the
switching section 313 easily understandable. Alternatively, switching may
also be done by means of software. For example, when the CPU 301 of the
player 300 or a decoder chip, in which the HD decoder 3140 and the SD
decoder 3150 are integrated together, executes a software program, the
switching section 313 may be realized as a part of branch decision
processing, which is carried out to determine whether decoder to function
is the HD decoder 3140 or the SD decoder 3150.

[0130]Since a video or audio content stored at its associated definition
in each of the high-density storage layer 102 and the low-density storage
layer 104 is provided with its own copyright management information, the
best possible method of copyright management can be provided.

[0131]The user input I/F 316 is in charge of exchange of information
between the user and the player 300, while the connection I/F 318 is in
charge of exchange of information between the TV set 320 and the player
300.

[0132]The user input I/F 316 is used when the user is inputting
performance information that specifies the display performance of the TV
set 320 using a remote controller, for example. As used herein, the
"performance information" means information that specifies a signal
format acceptable for the TV set 320. In this preferred embodiment, the
performance information is supposed to be a piece of information that
specifies a video signal format. Specifically, the performance
information may be a piece of information indicating whether the TV set
320 has the ability to display both HD video and SD video or the ability
to display only SD video, for example.

[0133]Meanwhile, the connection I/F 318 is compliant with the HDMI
standard and can keep up bidirectional communications with the TV set
320. Specifically, the connection I/F 318 requests the performance
information from the TV set 320, which sends its own performance
information to the connection I/F 318 in response to the request. These
processing steps are carried out automatically compliant with the
standard and the user does not have to do anything about that.

[0134]The format memory 317 stores information that defines the format of
the signal to be output from the player 300 (which will be referred to
herein as "output defining information"). The format memory 317 may be a
rewritable EEPROM. Once set, the format memory 317 retains the output
defining information even if the player 300 is turned OFF after that.

[0135]The output defining information is generated by the CPU 301 based on
the performance information of the TV set 320 that has been acquired by
way of the user input I/F 316 and the connection I/F 318. In this
preferred embodiment, if the performance information indicates that the
TV set has the ability to display both HD video and SD video, a value
indicating BD is stored. On the other hand, if the performance
information indicates that the TV set has the ability to display only the
SD video, then a value indicating SD is stored. It should be noted that
when the player 300 is shipped, a value indicating "automatic detection"
is stored as the output defining information.

[0137]The connection I/F 318 receives the output of the copyright
information processing section 319 and the output of the expanding
section 3142 or 3152, multiplexes these outputs together, and then send
the multiplexed stream to the TV set 320. Optionally, an additional
component for receiving these outputs, multiplexing them together and
sending the multiplexed data stream to the connection I/F 318 may be
provided. In that case, the connection I/F 318 will receive the
multiplexed data stream and send it to the TV set 320.

[0138]Hereinafter, it will be described with reference to FIGS. 5 through
9 how the player 300 operates.

[0139]FIG. 5 shows the procedure of initializing processing to be carried
out by the player 300. This processing is performed to determine from
which layer information should be read earlier, the high-density storage
layer 102 or the low-density storage layer 104, when the player 300 is
loaded with the optical disk 100. That is why this processing is carried
out when the user turns the player 300 ON for the first time or when the
player 300 is loaded with a hybrid disk for the first time. However, the
user can get this processing done at his or her desired time by
manipulating a remote controller (not shown), for example.

[0140]First, in Step S51, the CPU 301 gets an initializing screen
displayed on the TV 321. The data of the initializing screen may be
stored in the general-purpose memory 302, for example, and may be output
by way of the connection I/F 318 to the TV set 320 in accordance with the
instruction given by the CPU 301.

[0141]Next, in Step S52, the CPU 301 reads the output defining information
from the format memory 317 and shows the result on the initializing
screen.

[0142]FIG. 6 shows an exemplary initializing screen. On the screen, three
options 61, 62 and 63 are shown. As described above, when the player 300
is shipped, a value indicating "automatic detection" is stored in the
format memory 317. For that reason, the option 61 is now highlighted.

[0143]Referring back to FIG. 5, it can be seen that the processing path
branches in Step S53 according to the option 61, 62 or 63 that has been
picked by the user.

[0144]Specifically, in Step S53, the CPU 301 determines whether the option
picked by the user is "automatic detection" or not. If the answer is YES,
the process advances to Step S54. Otherwise, the process advances to Step
S55.

[0145]The processing steps that begin with Step S54 are carried out by the
CPU 301 to automatically determine from which of the two storage layers
102 and 104 of the optical disk 100 information should be read earlier.
In Step S54, the CPU 301 instructs the connection I/F 318 to get the
performance information of the TV set 320 (more specifically, the
definition of the TV 321) following the procedure defined by the HDMI
standard.

[0146]Next, in Step S56, it is determined based on the performance
information whether or not the TV 321 has the ability to display only SD
video (i.e., whether the TV has standard definition or not). If the
answer is YES, the process advances to Step S57. Otherwise (i.e., if the
TV has high definition), then the process advances to Step S58.

[0147]In Step S57, the CPU 301 stores a value indicating DVD as the output
defining information in the format memory 317. On the other hand, in Step
S58, the CPU 301 stores a value indicating BD as the output defining
information in the format memory 317.

[0148]Meanwhile, in Step S55, the CPU 301 determines whether the option
picked by the user is BD or not. If the answer is YES, the process
advances to Step S58. Otherwise (i.e., if the option picked by the user
is DVD), then the process advances to Step S59. The processing step S59
is the same as the processing step S57, and the description thereof will
be omitted herein.

[0149]When the output defining information is stored in the format memory
317 as a result of the processing described above, the CPU 301 reads the
video or audio information from the selected storage layer of the optical
disk 100 in accordance with that information. Once the output defining
information has been set, the playback processing may be carried out in
accordance with that information until the processing shown in FIG. 5 is
performed again.

[0150]Alternatively, another option "always detect automatically" may be
provided and the CPU 301 may perform the processing steps S54, S56, S57
and S58 every time the optical disk 100 is inserted. Then, even if the
user that has viewed programs on the TV 321 of the standard definition
has newly purchased a high definition TV, he or she can enjoy HD video
and audio without changing the settings of the player 300.

[0151]Hereinafter, it will be described with reference to FIG. 7 how the
player 300 performs the playback processing.

[0152]FIG. 7 shows the procedure of playback processing to be carried out
by the player 300.

[0153]First, in Step S71, the CPU 301 detects the insertion of a disk
based on a signal supplied from a sensor (not shown), for example. As
described above, the player 300 can retrieve information from not only a
hybrid disk (such as the optical disk 100) but also DVDs and BDs as well.
That is why it should be determined, through the processing steps that
follow Step S71, which type of disk has been inserted.

[0154]Next, in Step S72, the CPU 301 activates the optical pickup 310 to
get a light beam emitted, and then gets the light beam focused at the
same depth as that of the high-density storage layer 102, i.e., at a
depth of 0.1 mm as measured from the disk surface on the light beam
incoming side. In this case, the light beam has a wavelength of about 405
nm.

[0155]Next, in Step S73, the layer recognizing section 311 measures the
reflectance of the light beam, for example, thereby determining whether
or not there is any storage layer at that depth. If the answer is YES,
the process advances to Step S74. In that case, the optical disk inserted
is either the optical disk 100 or a BD. If there is no storage layer,
however, the process advances to Step S75.

[0156]In Step S74, the CPU 301 moves the optical pickup 310 to around the
innermost area of the optical disk to determine whether or not the hybrid
information 21 is stored at a predetermined location in the lead-in. If
the answer is YES, the process advances to Step S76. Otherwise, the
process advances to Step S78. If there is the hybrid information 21, then
the given optical disk is recognized as the optical disk 100. If not, the
given optical disk is recognized as a BD.

[0157]In Step S76, the CPU 301 makes the optical pickup 310 read the
hybrid information 21. Then, in Step S77, the CPU 301 analyzes the hybrid
information 21 to determine whether or not there is a low-density storage
layer.

[0158]If the answer is YES, the process advances to Step S79. In that
case, a message like "this optical disk is a hybrid disk" is either shown
on the screen or output through the loudspeakers, thereby notifying the
user of the fact. As a result, he or she can know that the given optical
disk is a hybrid one, i.e., there are a high-density storage layer and a
low-density storage layer in it. On the other hand, if there is no
low-density storage layer, the process advances to Step S78. In that
case, a message like "this optical disk is a BD" may be either shown on
the screen or output through the loudspeakers to notify the user of the
fact.

[0159]The information of the messages to be presented may be stored in the
general-purpose memory 302, for example. The CPU 301 reads that
information out and sends it out to either the TV 321 or the loudspeakers
322 via the connection I/F 318.

[0160]In Step S78, the optical pickup 310 reads information from either
the high-density storage layer 102 or BD's storage layer of the optical
disk 100, on which the light beam has already been focused, and displays
that information. That is to say, the optical pickup 310 gets audio/video
information decoded by the HD decoder 3140 and output to the TV 321 and
the loudspeakers 322. After that, the process ends.

[0161]In Step S79, it is determined whether or not the output defining
information has a value indicating "BD". If the answer is YES, the
process advances to Step S78. Otherwise (i.e., if the information has a
value indicating "DVD"), the process advances to Step S75.

[0162]In Step S75, the CPU 301 activates the optical pickup 310 to get a
light beam emitted, and then gets the light beam focused at the same
depth as that of the low-density storage layer 104, i.e., at a depth of
0.6 mm as measured from the disk surface on the light beam incoming side.
In this case, the wavelengths of the light beam are changed into about
650 nm.

[0163]Next, in Step S80, the layer recognizing section 311 measures the
reflectance of the light beam, for example, thereby determining whether
or not there is any storage layer at that depth. If the answer is NO, the
process advances to Step S81. On the other hand, if the answer is YES,
the process advances to Step S82. In that case, the optical disk inserted
is either the optical disk 100 or a DVD.

[0164]In Step S81, retry processing is carried out because it is
determined that the type of the given disk must have been recognized by
mistake, and then the process goes back to Step S72. If no storage layer
can be detected from the disk inserted even by performing the retry
processing a predetermined number of times, the process may end.

[0165]In Step S82, the optical pickup 310 reads information from either
the low-density storage layer 104 or DVD's storage layer of the optical
disk 100, on which the light beam has already been focused, and displays
that information. In this case, the optical pickup 310 gets audio/video
information decoded by the SD decoder 3150 and output to the TV 321 and
the loudspeakers 322.

[0166]It should be noted that the video and other types of information
presented to the user change depending on whether the information is read
out from the low-density storage layer 104 of the optical disk 100 or the
DVD's storage layer thereof. Hereinafter, the playback process to be
performed on the low-density storage layer 104 will be described with
reference to FIGS. 8 and 9.

[0167]In the following description, the processing shown in FIGS. 8 and 9
is supposed to be carried out by the player 300. However, the statement
of this processing is also applicable to even a situation where a
conventional read-only DVD player is performing playback processing on
the low-density storage layer 104 as a normal DVD's storage layer. The
effects caused by the method shown in FIGS. 8 and 9 are achieved most
significantly when the playback operation is carried out using such a DVD
player.

[0168]FIG. 8 shows the procedure of information retrieval processing on
the low-density storage layer 104. To start this processing, first, the
physical control information stored in the lead-in 211 of the low-density
storage layer 104 is read out and predetermined pre-processing is
performed.

[0169]First, in Step S85, the CPU 301 instructs the optical pickup 310 to
read the navigation information 2122 from the data area 212 and execute
First Play PGC, which is a type of processing that is always carried out
first when data is read from the data area 212 of the low-density storage
layer 104.

[0170]The low-density storage layer 104 of the optical disk 100 is
designed such that an image including the HD presence information 2125 is
presented in the First Play PGC. That is why when starting to read
information from the low-density storage layer 104, the player 300
presents the user an image indicating the presence of the high-density
storage layer 102 (more specifically, an image indicating the presence of
HD audio/video information) as a part of the video.

[0171]FIG. 9 shows an exemplary on-screen message indicating the presence
of the high-density storage layer 102. By reading this message, the user
knows that HD video can be viewed if a player that can retrieve
information from the high-density storage layer and an HDTV are used in
combination. If he or she uses the player 300 and an HDTV, he or she can
get the initializing screen shown in FIG. 6 displayed and can change the
types of processing such that information can be retrieved from the
high-density storage layer 102. On the other hand, if the user uses a
read-only DVD player, he or she can sense that an HD title is also
included in the optical disk 100 and will be able to enjoy the HD title
when he or she purchases a BD player and an HDTV sometime in the future.

[0172]It should be noted that the on-screen message including the HD
presence information 2125 does not always have to be presented during the
sequence of First Play PGC itself. Alternatively, when the processing
branches in accordance with a command that must be executed when First
Play PGC ends, that on-screen message may be presented during a sequence
executed after the branch. Optionally, the light beam may be focused on
the low-density storage layer 104 first unlike the example shown in FIG.
7 and that piece of information may be presented during the processing
that is carried out substantially earliest.

[0173]After that, the process advances to Step S86, in which an SD title
starts to be played back. More specifically, a menu is displayed in Step
S861 and the main content is played back in Step S862. After that, the
process ends.

[0174]The player 300 of this preferred embodiment operates as described
above. In the first half of the processing through the processing steps
S74, S76 and S77 shown in FIG. 7, there is no need to detect both the
high-density storage layer 102 and the low-density storage layer 104 by
focusing the light beam on both of these layers. That is why compared to
the situation where both of these layers need to be detected by actually
focusing the light beam on both of them, the processing can be done much
more quickly.

[0175]Furthermore, in the processing step S79 described above, if the
optical disk 100 inserted includes the high-density storage layer 102 and
the low-density storage layer 104, it is determined by the output
defining information whether information should be retrieved from the
high-density storage layer 102 or the low-density storage layer 104. And
in the processing steps that follow the processing step S79, information
is retrieved in accordance with the decision. As to the storage layer to
retrieve information from, the output defining information determines it
with not only the user's playback environment but also his or her
preference taken into consideration. That is why the player 300 can
quickly start retrieving the information that can be viewed and listened
to by the user and that has been requested by him or her.

[0176]Even if the player 300 has the function of down-converting HD
audio/video into SD audio/video, the function need not be used when the
player 300 is loaded with the optical disk 100. This is because the
player 300 has already recognized the presence of the low-density storage
layer 104 in Step S77 and can control its operation so as to read and
present the SD audio/video from the low-density storage layer 104. For
that reason, only when loaded with a BD, the player 300 may use its
down-converting function.

[0177]In the foregoing description of preferred embodiments, the same
content is supposed to be stored with different qualities in the
high-density storage layer 102 and the low-density storage layer 104 of
the optical disk 100. That is why unless otherwise specified by the user,
the player 300 is supposed to retrieve the HD title information 2023 from
the high-density storage layer 102 preferentially in an environment where
the information can be displayed with HD quality, but retrieve the SD
title information 2123 from the low-density storage layer 104 in an
environment where the information can be displayed only with the SD
quality (see the processing steps S56 to S58 shown in FIG. 5 and the
processing steps S78 and S79 shown in FIG. 7).

[0178]As the case may be, however, two different contents may be stored on
the high-density storage layer 102 and the low-density storage layer 104,
respectively. For example, a movie content of HD quality may be stored on
the high-density storage layer 102 and a bonus content of that movie such
as the filmmaking process audio and video of that movie of SD quality may
be stored on the low-density storage layer 104. Or a movie content of HD
quality may be stored on the high-density storage layer 102 and a bonus
content of SD quality that has nothing to do with that movie may be
stored on the low-density storage layer 104.

[0179]In that case, even if HD video is played back based on the HD title
information 2023 stored on the high-density storage layer 102, the user
is preferably notified that there is the low-density storage layer 104
and that a different content is stored there. Thus, a new data structure
will be proposed with reference to FIG. 10.

[0180]FIGS. 10(a) and 10(b) show other exemplary data structures for the
high-density storage layer 102 and low-density storage layer 104. The
data structure of the high-density storage layer 102 shown in FIG. 10(a)
is different from that shown in FIG. 2(a) in that SD presence information
2025 is further stored in the data area 202 of the high-density storage
layer 102.

[0181]The SD presence information 2025 is provided as audio/video
information indicating that there is the low-density storage layer 104
and/or that an SD quality content is stored separately from an HD quality
content. This SD presence information 2025 is presented at an arbitrary
time before the HD title information 2023 starts to be displayed or after
the HD title information 2023 has been displayed. Its timing (i.e.,
presentation order) is defined by the navigation information 2022, for
example.

[0182]On the other hand, the data structure of the low-density storage
layer 104 shown in FIG. 10(b) is the same as that shown in FIG. 2(b).
However, the audio/video information stored as the HD presence
information 2125 may have different contents from the message displayed
in FIG. 9. For example, audio/video information, indicating that the
content stored on this storage layer is just a bonus content and that the
main content could only be played back with a BD player, may be stored as
the HD presence information 2125. When starting to retrieve information
from the high-density storage layer 102, the player 300 reads the hybrid
information 21 to confirm whether or not there is the low-density storage
layer 104. If the information indicates the presence of the low-density
storage layer 104, then the SD presence information 2025 is read out from
the high-density storage layer 102 and a video signal and/or an audio
signal, indicating the presence of the low-density storage layer 104 or
the presence of SD audio/video, is output to the TV 321.

[0183]FIG. 11(a) shows an exemplary on-screen message indicating the
presence of the low-density storage layer 104. The DVD layer shown in
FIG. 11(a) corresponds to the low-density storage layer 104. In this
example, the user is prompted to decide from which layer the information
should be retrieved, the BD layer or the DVD layer. In selecting the BD
layer, he or she needs to highlight the box 111 using a remote controller
(not shown) and then enter his or her selection. On the other hand, in
selecting the DVD layer, he or she needs to highlight the box 112 using
the remote controller (not shown) and then enter his or her selection. In
FIG. 11(a), the box 112 is now highlighted. Then, the player 300
retrieves information from the selected storage layer. If necessary, the
CPU 301 instructs the optical pickup 310 to change the wavelengths of the
light beam or tells the layer specifying section 312 which storage layer
to read information from. In accordance with this instruction, the layer
specifying section 312 changes the storage layers on which the light beam
should be focused. Also, as in the example described above, the layer
specifying section 312 may switch the transmission lines of the read
signal supplied from the signal switching section 313 into that leading
to the SD decoder 3150.

[0184]It should be noted that the message shown in FIG. 11(a) is just an
example and a different message could tell the user that this is a hybrid
disk. For example, FIG. 11(b) shows an exemplary on-screen message
notifying the user that there is a standard quality content. In the
example shown in FIG. 11(b), the information about the main content of a
movie is supposed to be stored on the high-density storage layer 102,
while a bonus content thereof is supposed to be stored on the low-density
storage layer 104.

[0185]According to this notification method, the user knows the presence
of the bonus content and indirectly senses the presence of the
low-density storage layer 104. As the user does not have to pay attention
to the fact that this is a hybrid disk, this method is easily
understandable for a user of any age. By highlighting one of the boxes
113 and 114, showing the types of contents to view and listen to, using a
remote controller (not shown) and entering his or her selection, he or
she can select either the BD layer or the DVD layer indirectly.

[0186]The exemplary messages shown in FIGS. 11(a) and 11(b) are presented
by the player 300 based on the SD presence information 2025. To compose
these messages, the SD presence information 2025 includes graphic data
defining the figures of the boxes to be highlighted. In many cases, a
figure to be highlighted is superimposed on a background image, which is
compressed image data. These data are expanded and then presented by the
HD decoder 3140.

[0187]In the description of this preferred embodiment, the graphic data
associated with the box 112 or 114 is linked to a command instructing
that layers be switched into the low-density storage layer and
information be retrieved from that layer. By executing this command, the
CPU 30 performs the processing described above. This command may be
stored as a part of the SD presence information. Alternatively, the
command may also be included in the navigation information 2022, for
example.

[0188]Also, if the player 300 can retrieve information from the
high-density storage layer 102, another HD presence information (not
shown) may be further stored on the low-density storage layer 104 in
addition to the HD presence information 2125 and the player 300 may
display the messages shown in FIGS. 11(a) and 11(b) based on that
additional HD presence information. As a result, the user can view and
listen to any content he or she likes by switching the BD and DVD layers
one into the other. In that case, however, to prevent a conventional
player that can retrieve information from only a DVD layer (i.e.,
low-density storage layer) from malfunctioning, the additional HD
presence information should be stored in an optical disk area that the
conventional player never accesses, for example.

[0189]In the preferred embodiments described above, the performance
information of the TV set 320 is supposed to be acquired automatically
through the HDMI interface and the result is supposed to be stored in the
video output format memory 317. Alternatively, the performance
information may always be set by the user by default on the initializing
screen. In that case, the present invention would be applicable to even a
player with no bidirectional interface or to a TV 320 without any
bidirectional interface.

[0190]Also, in the preferred embodiments described above, the hybrid
information 21 is supposed to be stored in the lead-in of the
high-density storage layer 102. However, this is just an example.
Alternatively, multiple pieces of hybrid information 21 may be stored on
the header information portion of a sector, which is the minimum storage
unit of the optical disk.

[0191]Furthermore, in the preferred embodiments described above, one
high-density storage layer 102 and one low-density storage layer 104 are
supposed to be included in the optical disk 100. However, the present
invention is in no way limited to those specific preferred embodiments.
Optionally, multiple high-density storage layers 102 and/or multiple
low-density storage layers 104 may be present on the optical disk 100.

[0192]Furthermore, in the preferred embodiments described above, a
disklike optical disk is supposed to be used. However, this is also only
an example. Alternatively, a card from/on which data can be read and
written optically may also be used instead.

INDUSTRIAL APPLICABILITY

[0193]An optical storage medium according to the present invention
includes two storage layers with mutually different storage densities. On
one of these two storage layers, management information indicating the
presence of the other storage layer is stored. And if the player notifies
the user of the presence of the other storage layer based on the
management information, he or she can sense the presence of that layer
easily. Consequently, by using the optical storage medium of the present
invention and the player of the present invention that can retrieve
information from such an optical storage medium, the user can retrieve
his or her desired information much more easily and handily.